Bernese GPS Software Version 4.2

Transcription

1 ASTRONOMICAL INSTITUTE UNIVERSITY OF BERNE Bernese GPS Software Version 4.2 Edited by U. Hugentobler, S. Schaer, P. Fridez Contributors: G. Beutler, H. Bock, E. Brockmann, R. Dach, P. Fridez, W. Gurtner, U. Hugentobler, D. Ineichen, J. Johnson, M. Meindl, L. Mervart, M. Rothacher, S. Schaer, T. Springer, R. Weber February 2001

2 Documentation of the Bernese GPS Software Version 4.2 February 2001 Please send comments on the Bernese GPS Software and this manual as well as requests for copies to: Dr. Urs Hugentobler Phone : Astronomical Institute Fax : University of Berne Sidlerstrasse 5 CH-3012 Berne Switzerland For contact and support send an to: Pierre Fridez Phone : "! #$

3 Table of Contents List of Figures List of Tables XIII XVII 1. Introduction and Overview Philosophy Behind the Bernese GPS Software Main Objectives and General Characteristics Program Structure and Functional Flow Diagram Observables and Linear Combinations Parameter Estimation Accuracy and Performance GPS and GLONASS Basic Facts GPS Satellites and Their Constellation The Satellite Signal Signal Processing The GLONASS System GLONASS Satellites and Their Constellation The Signals of the GLONASS Satellites IGEX and IGLOS: Global GLONASS Campaigns The Menu System Introduction Bernese GPS Processing Programs The Bernese GPS Menu System for DOS, VMS, and UNIX Structure of the Menu System Starting the Menu System Preparing the Environment (LOADGPS) Calling the Menu System Panels Program Panels Data Panels Help Panels Selections Menu Selections Option Selections in Data Panels File Selections Bernese GPS Software Version 4.2 Page I

4 Table of Contents 3.5 Special Menu Commands Job Submission and Job Output Handling Submit Jobs Job Output Error Handling Error Message File Return Codes Semi-Automated Processing Calling Programs Without the Menu System User-Specific Additions to the Menu System Technical Details Command Files pgmnam.bat (DOS), pgmnam.com (VMS and UNIX) Command file pgmnam.ctl Command File SUBJOB.COM (VMS), SJ (UNIX) Skeleton Files Processing Examples Example 1: Regional Campaign Example 2: Local Campaign Example 3: Rapid Static Positioning Processing and Naming Defaults Campaign Setup External Data Sources and Data Transfer Transfer to RINEX RINEX: The Receiver-Independent Exchange Format RINEX Observation Files RINEX Navigation Message Files RINEX Meteorological Data Files Data Conversion to RINEX Transfer RINEX Bernese Transfer RINEX Bernese Transfer Bernese Rinex The SINEX Format Definition of the SINEX Bernese NEQ File SINEX SINEX Bernese NEQ File Generating Bernese NQ0 Files from SINEX and NEQ Files External Data Sources CODE Products IGS Products Satellite Orbits Motivation Basic Theory Celestial Mechanics Page II AIUB

5 Table of Contents The Keplerian Orbit The Osculating Orbit Elements Orbit Parameterization (Deterministic Part) Orbit Parameterization (Pseudo-Stochastic Part) Variational Equations Numerical Integration The Orbit Programs of the Bernese GPS Software Version Using Orbit Information with Version Case (a): Programs BRDCHK, BRDTST, and SATCLK Using Precise Orbits (Program PRETAB) Program ORBGEN for Cases (a) and (b) Service Programs STDPRE and STDDIF Estimating Orbits with Version 4.2 (Case (c)) Using Combined GPS and GLONASS Data (Case (d)) Experiences Made With the Bernese GPS Software at CODE CODE IGS Analysis Center Questionnaire Observation Equations Phase Pseudoranges Code Pseudoranges Receiver Clocks Measurement Biases Forming Differences Linear Combinations of Observations Ionosphere-Free Linear Combination Geometry-Free Linear Combination Wide-Lane Linear Combination Melbourne-Wübbena Linear Combination Data Pre-Processing Overview Pre-Processing on the RINEX Level Pre-Processing of Code Observations Simple Non-Parametric Screening (CODCHK) Single Point Positioning and Receiver Clock Synchronization (CODSPP) Forming Baselines Pre-Processing Phase Observations Screening of Post-Fit Residuals Marking of Observations Station Coordinates and Velocities Reference Frames Coordinate Estimation Pseudo-Kinematic Coordinate Estimation Site Displacements Coordinate Comparisons Merging Coordinate Files Bernese GPS Software Version 4.2 Page III

6 Table of Contents 12.Troposphere Modeling and Estimation Motivation Theory Using Ground Meteorological Data Introducing Troposphere Data Into the Processing Tropospheric Delay Estimation Local Troposphere Models Troposphere Parameters for Individual Stations Estimation of Troposphere Gradients Elevation-Dependent Weighting of Observations How to Retrieve Best Possible Zenith Delay Estimates Tropospheric SINEX Format Ionosphere Modeling and Estimation Subdivision of the Atmosphere Motivation and Introductory Remarks Choice of the Linear Combination Impact of Unmodeled Ionosphere on Single-Frequency GPS Solutions How to Treat Small-Area High-Precision Arrays Theory Introduction Characterizing the Ionosphere Influence of the Ionosphere on Various Linear Combinations Ionospheric Effects on GPS Signals Ionosphere Modeling Deterministic Component Differential Code Biases (DCBs) Ionosphere Mapping on Zero- and Double-Difference Level Local TEC Model Global TEC Model Station-Specific TEC Models Stochastic Component Estimation of Deterministic Ionosphere Models Local Ionosphere Models Global, Regional, or Station-Specific Ionosphere Models Application of Deterministic TEC Models Stochastic Ionosphere Modeling Technique Estimation of Stochastic Ionosphere Parameters Using Stochastic Ionosphere Parameters Earth Orientation Modeling and Estimation Motivation Theory Use of Earth Orientation Parameters in the Bernese GPS Software General Dataset Names Update of Pole Information Estimation of Earth Orientation Parameters Page IV AIUB

7 Table of Contents Options in GPSEST Options in ADDNEQ Initial Phase Ambiguities and Ambiguity Resolution Motivation Theory Ambiguity Resolution Algorithms NO Algorithm ELIMIN Algorithm ROUND Algorithm SIGMA Algorithm SEARCH Algorithm QIF (Quasi-Ionosphere-Free) Algorithm The Role of the Ionosphere Implementation of the QIF Strategy Ambiguity Resolution Strategies Resolving GLONASS-Related Ambiguities Processing Undifferenced Data Cleaning of Undifferenced Data Data Screening Based on Melbourne-Wübbena Linear Combination Data Screening Based on Geometry-Free Linear Combination Data Screening Based on Ionosphere-Free Linear Combination Code Smoothing Reliability and Possible Enhancements Processing Undifferenced GPS Data ZD Pre-Processing ZD Processing Precise Point Positioning Processing SLR Data Example of Processing Undifferenced Data Clock Files in the Bernese GPS Software Satellite Clocks Receiver Clocks Clock Input in Other Programs Antenna Phase Center Offsets and Variations Motivation Satellite Antenna Phase Centers Receiver Antenna Phase Centers and Their Variations Estimation of the Receiver Antenna Phase Center Variations Combination of Solutions Motivation Basic Theory of Least-Squares Estimation Least-Squares Estimation Parameter Pre-elimination Sequential Least-Squares Estimation Bernese GPS Software Version 4.2 Page V

8 Table of Contents Common Adjustment Sequential Least-Squares Adjustment Computation of the Combined RMS Special Features of Combining Normal Equations Constraining Parameters Introducing Additional Parameters Independence of the A Priori Information Free Network Constraints Reduction of the Number of Unknown Parameters Limitations of NEQ Stacking Applications and Strategies Using Normal Equations The Combination Programs ADDNEQ and COMPAR Combination Program COMPAR Combination Program ADDNEQ General Introduction Differences to GPSEST Free Coordinate Solutions Fixing Coordinates or Velocities on Special Values Site Velocity Estimation Tuning Troposphere Estimates Output Description Handling Parameters and NEQ Files in Programs GPSEST and ADDNEQ Stacking of Normal Equations Using the New ADDNEQ2 Program Time-Dependent Parameters Piece-Wise Constant Function Piece-Wise Linear Function Parameter Manipulations Changing the Auxiliary Parameter Information Rescaling the Normal Equation Matrices A priori Transformation of Coordinates Into a Different Reference Frame Changing the A Priori Values Changing the Validity Interval Parameter Elimination Parameter Stacking Constraining of the Parameters Constraining Parameters to Their A Priori Values Constraining Ellipsoidal Coordinates Relative Constraints of Station Coordinates and Velocities Free Network Conditions Continuity Condition (SINEX) Expansion of the Normal Equation System Estimation of Station Velocities Changing the Parameter Description for SINEX Input Options of the Program ADDNEQ Data Simulation and Variance-Covariance Studies 319 Page VI AIUB

9 Table of Contents 20.1 Principles of Data Simulation Models Used for Data Simulation Stochastic Properties Deterministic Models Essential Input Files Services Observations and File Headers Residuals Extractions Conversions Delete Files Bernese Processing Engine (BPE) Introduction Getting Started LOADGPS LOADGPS Command Line Arguments Getting Around The CPU File (PCFCTL.CPU) System Administration Notes Directory Structure Directory Trees The Process Control Script (PCS) How the PCS Works Format of Protocol File The Process Control File (PCF) Linear PCFs Parallel PCFs Running a PCS An Example PCF Running Bernese Programs in BPE Scripts The Panel Files Panel Variables Parallel Scripts The Clean Script Starting PCS From the Shell or System Prompt BPE Menu Items PANEL UPDATE PANEL EDITING Panel Editing FIX Option Panel Editing UPDATE Option Panel Editing COPY Option PREPARE RINEX SPECIAL FILES BPE PROCESSING BPE SERVICES Bernese GPS Software Version 4.2 Page VII

10 Table of Contents 22.8 BPE Scripts Skeleton Script The RUN_PGMS Script The PUTKEYWE Script BPE Special Programs GPSWIND PRSLIN PRSLINF BPE Example Program Structure Introduction Overview of the Program Structure Summary of the GPS/GLONASS Main Programs Flow Diagrams and Decompositions Programming Standards and Conventions Maximum Dimensions and Commons Recompilation of Particular Programs Data Structure Introduction Overview of the Data Structure Overview of the Data Files General Files Constant File Geodetic Datum Information Receiver Characterization File Receiver/Antenna Name Translation File Antenna Phase Center Offsets and Patterns Geopotential Coefficients Pole Coordinates Pole Offsets for the C04 and Rapid Pole Series SINEX General Information File IONEX General Information File Satellite Information File Satellite Problem File Station Problem File Station Problem File (New Format) Raw Data and RINEX Files Observation Files General Remarks Code/Phase Zero/Single-Difference Header/Observation Files Orbit Files Satellite Broadcast Messages Precise Ephemerides in IGS Format Tabular Orbits Standard Orbits Page VIII AIUB

11 Table of Contents Radiation Pressure Coefficient File Improved Orbit Parameters Miscellaneous Files Station Coordinates Station Eccentricity Elements Station Velocities Station Name Translation Table Variance-Covariance Matrix Residual Files Program Output Files Normal Equation Files Normal Equation Files (New Format) List Files Plot File Pole File in IERS Format SINEX File Normal Equation Rescaling File Observation Editing File Delete Files Summary Files Single Point Positioning File Meteo and Water Vapor Radiometer Data Troposphere Parameter File Tropospheric SINEX File Ionosphere Models Ionosphere (IONEX) Maps Satellite Clock Coefficients Receiver Clock Coefficients Differential P1-P2 Code Biases for Satellites and Receivers Antenna Height Translation Table Ocean Loading Table Baseline Definition File Cluster Definitions (Input) Cluster Definitions (Output) Special Fixed (and Constrained) Station File Special Fixed Troposphere File Special FTP File Receiver Antenna Orientation File Program-Specific Files Installation Guide Installation Guide for the PC-Version Overview Hardware Requirements Software Requirements Operating System Compilers Bernese GPS Software Version 4.2 Page IX

12 Table of Contents Configuration of the DOS Environment System Configuration Files CONFIG.SYS and CONFIG.NT Drive Letter Substitution Creation of a DOS Window Under Windows 9x Systems Creation of a DOS Window Under Windows NT Systems Installation of the Bernese GPS Software Version Installation From CD-ROM Installation of ftp Version Configuration of the Software Before Running it Loading the Environment: File LOADGPS.BAT Directory Listing Format: File FORMAT.DAT Compiling/Linking Bernese GPS Software Version Hints and Tips User Supplied Editor and Browser Background Colors of the Data Panels Individual User Subdirectories Upgrade From Earlier Versions to Version Processing Examples Trouble Shooting Installation Guide for the VAX-Version Requirements on VAX/Alpha Systems Copying the Installation Files on Disk CD-ROM FTP Version Installation of all Files File Installation File Source Code Changes Adjustment of the Size of Executables User-Supplied Editor Display Mode for Data Input Panels Campaign List Compiling and Linking Hints and Tips Installation of Load Modules Installation of the User Environment Setting up the BPE Processing Examples Installation Guide for the UNIX Version Requirements on UNIX Systems Copying the Installation Files onto Disk CD-ROM Version FTP Version Installing all Source Code and Miscellaneous Files Source Code Changes Adjustment of the Size of Executables Campaign List Page X AIUB

13 Table of Contents Compiling and Linking the Source Code Hints and Tips Use of JPL Ephemerides for Moon, Sun, and Planets Installation of Load Modules Automatic Installation of the Environment for Additional Users Manual Installation of the Environment for Additional Users Setting up the BPE Processing Examples Bibliography 505 Index 511 Bernese GPS Software Version 4.2 Page XI

14 Table of Contents Page XII AIUB

15 List of Figures 1.1 Functional flow diagram of normal processing in Bernese GPS Software Version GPS orbits (Earth and orbital planes in scale) GPS Block II satellite Biphase modulation of the GPS signal GLONASS satellite Ground track of GLONASS satellite (110) compared to the ground track of GPS satellite (6) for the time interval of one sidereal day The IGEX observation network as used by the CODE analysis center Comparison of broadcast GLONASS orbits and CODE precise orbits with SLR measurements Menu system top level LOADGPS.BAT: Preparing the environment (DOS) Menu system startup file for DOS Left part of program panel Right part of program panel Left part of a data panel Right part of data panel Example: General file selection panel Example: Observation file selection panel DOS example: VMS example: UNIX example: Sample skeleton file for file (extract) Sample file (extract) Stations used in campaign 4.2 Stations used in campaign RINEX observation file (GPS) RINEX navigation message file (GPS) RINEX meteorological data file N-file of program SNXNEQ N-file of programs SNX2NQ0 and NEQ2NQ The set of orbital elements "!#$% &'"(*) Osculating semimajor axis of PRN 14 during three days of year Osculating eccentricity of PRN 14 during three days of year Bernese GPS Software Version 4.2 Page XIII

16 List of Figures 8.4 Osculating inclination of PRN 14 during three days of year Osculating r.a. of ascending node of PRN 14 during three days of year Osculating argument of perigee of PRN 14 during three days of year Osculating semimajor axis of PRN 14 over three years Menu for orbit programs in the Bernese GPS Software Version Flow diagram of the orbit part in the Bernese GPS Software Version Orbit characterization for one-day arcs in program GPSEST Stochastic parameter selection in program GPSEST Orbit characterization in program ADDNEQ Stochastic parameter selection in program ADDNEQ Additional stochastic parameter selection in program ADDNEQ IGS permanent tracking network Orbit quality of the IGS analysis centers Functional flow diagram of the processing part in the Bernese GPS Software Tilting of the tropospheric zenith by the angle Chapman curve of ionization rate Monthly and monthly-smoothed sunspot numbers Single-layer model PRN-specific P1-P2 DCB estimates as computed by CODE Coordinate and ambiguity parameters as function of SIP constraining Example of an ionosphere file containing (two) local TEC models Zero-degree TEC parameter )") extracted from local ionosphere models Example for an ionosphere file containing a series of global TEC models hourly global TEC snapshots for February 12, 2001, as produced by CODE Mean TEC from January 1, 1995, extracted from CODE GIMs Stochastic ionosphere parameters (SIPs) describing the double-difference ionospheric delay on L Regional (or baseline-specific) ionosphere model Fractional parts of wide-lane ambiguities indicating the (remaining) deterministic part of the ionosphere Rms of a 7-parameter Helmert transformation with respect to the true coordinate set Orbit quality estimated from discontinuities at day boundaries (eclipsing and noneclipsing satellites) Satellite visibility plot for a short session and a short baseline Satellite visibility plot for a long session and a long baseline Ambiguities stored in single difference phase header file Search ranges in space Noise of the Melbourne-Wübbena combination under different AS conditions. Data of one station (Wettzell, Germany) collected during two days in 1997 is shown Code residuals from point positioning. Data from a receiver installed at USNO was used for day 133 of Page XIV AIUB

17 List of Figures 16.3 Clock output block in GPSEST general output file BPE processing steps for undifferenced processing example Trimble antennas: spherical harmonics development of degree 10 estimated from GPS data Combination of the normal equations of different processing steps Processing scheme based on baseline (or bluster) processing Panel options to define the geodetic datum of a solution The first option input ( Panel ) of ADDNEQ The option input ( Panel ) of ADDNEQ to modify the parameterization and the a priori constraints of the troposphere Error ellipses using the values of the GPSEST or ADDNEQ program output Plot of the baseline length residuals and the associated rms errors (in cm) derived from the ADDNEQ (or COMPAR) output Piece-wise constant function Modeling of time-dependent parameters by resp Changing the validity interval for the constant function Changing the validity interval for the linear function Reducing the number of parameters Continuity condition for the piece-wise linear function Addition of the new coordinate parameter NEQ system expansion for SINEX Output of the program ADDNEQ Process Control Script flow chart Program structure of the Bernese GPS Software Version Maximum dimension declaration of the main program COMPAR Common blocks defined in the main program COMPAR Data structure of the Bernese GPS Software Version File of all physical constants File of the geodetic datum definitions Receiver characterization file Receiver/antenna name translation ( ) file Antenna phase center offsets model (file, part 1) Elevation and azimuth dependence of the antenna phase centers according to model (file, part 2) The geopotential file Pole file ( ) in Bernese Format Pole offset file in Bernese format. The values are valid for the transformation of the C04 pole to the ITRF94 realization of the terrestrial reference frame General SINEX information file General IONEX information file Satellite information file (T means: ROCK Model T to be used as a priori radiation pressure model) Bernese GPS Software Version 4.2 Page XV

18 List of Figures Satellite problem file (example file ). The files SAT_yyyy.CRX are available in the anonymous FTP area in Berne Station problem file Station problem file (example file Observation files Example of an observation file (header in lines 1-45; observations in lines 47-57) Orbit files Broadcast messages ( File). 40 lines of information per message Precise orbit file in SP3 format ( file) Tabular orbit information ( file) Standard orbits ( file) File of a priori and estimated orbit parameters ( file) Coordinate ( ) file Station eccentricity ( ) file Site velocity ( ) file Station name translation ( ) file Variance-covariance ( ) file of type Example file ( ) Normal equation rescaling ( ) file Editing ( ) file Delete ( ) file CODSPP summary ( ) file Meteo ( ) file of type Meteo ( ) file of type Troposphere estimates in file format Tropospheric SINEX ( ) file Ionosphere ( ) file of model type Ionosphere ( ) file of model type Ionosphere ( ) file of model type Ionosphere (IONEX) map ( ) file Satellite clock ( ) file Receiver clock corrections (for simulation only) Differential P1-P2 code biases for GPS satellites ( file) Height translation ( ) file Ocean loading ( ) file Baseline definition ( ) file Cluster definition input ( ) file Cluster definition output ( ) file for one particular cluster Special fixed station ( ) file. Both entry types may also be used in the same file Special troposphere ( ) file Special FTP ( ) file Antenna orientation ( ) file Page XVI AIUB

19 List of Tables 1.1 Receiver types used by the Bernese GPS Software Parameter types implemented in the Bernese GPS Software Version Campaigns and permanent arrays processed with the Bernese GPS Software GPS constellation status Components of the satellite signal Broadcast clock parameters Broadcast ephemerides Comparison of the GLONASS with the GPS Bernese RINEX converters Auxiliary programs CODE products available through anonymous ftp Errors in baseline components due to orbit errors Estimated quality of orbits in Perturbing accelerations acting on a GPS satellite File of the Bernese GPS Software Version Sample output produced by program BRDTST Output produced by program ORBGEN with classical radiation pressure model using tabular positions stemming from broadcast messages Output produced by program ORBGEN with classical rpr model Output produced by program ORBGEN using full new orbit model Development of the CODE analysis using the Bernese GPS Software Linear combinations (LCs) of the and observables used in the Bernese GPS Software Version Extraction of CODSPP output (estimated GPS/GLONASS system time difference) Tropospheric zenith delay as a function of temperature T, pressure P, and relative humidity H Ionosphere-induced scale factor (per TECU) when neglecting the ionosphere Influences of the most important error sources on various linear combinations Ambiguity resolution strategies List of the Bernese GPS Software Version 4.2 main programs Bernese GPS Software Version 4.2 Page XVII

20 List of Tables 24.1 List of the Bernese GPS Software Version 4.2 data files Program-specific files Page XVIII AIUB

21 1. Introduction and Overview 1.1 Philosophy Behind the Bernese GPS Software The Bernese GPS Software is a sophisticated tool meeting highest quality standards for geodetic and further applications using the GPS as well as the GLONASS. This documentation is intended to give insight into theoretical aspects of GPS data processing, the working principles and concepts of the Bernese GPS Software, and the practical use of the package for a reader who already does have a basic knowledge of GPS data processing. The attendance of the Bernese GPS Software Introductory Course is presupposed. Despite the large number of pages of this documentation, not all issues related to GPS and GLONASS data processing may be highlighted and discussed. The reader may, however, get a good idea of possible analysis strategies which promise to meet his accuracy requirements for his particular applications. The Bernese GPS Software team offers support in case of users questions not covered by this documentation. 1.2 Main Objectives and General Characteristics The Bernese GPS Software is currently released as Version 4.2. In March 1988 the Bernese GPS Software Version 3.0, a software tool based on its predecessor Bernese Second Generation GPS Software was completed. Between 1988 and 1995 five major releases could be issued in order to take into account the rapid development in the field high accuracy applications of the GPS: release 3.1 was issued in December 1988, release 3.2 in April 1990, 3.3 in May 1991, 3.4 [Rothacher et al., 1993] in May 1993, and release 3.5 in February The Bernese GPS Software Version 4.2 is based on Version 4.0 (released September 1996), which in turn is based on Version 3. Version 4.2 may be used to process any campaigns which were processed with Version 4.0 (downward compatibility). The new components of Version 4.0 with respect to Version 3 were: Completely revised orbit part. The full new Bernese orbit model [Beutler et al., 1994] is available in Version 4.0. The new model is a generalization of the one used in Software Version 3. The processing program ADDNEQ may be used to combine normal equation systems generated with program GPSEST. ADDNEQ does not handle observations but normal equation systems. This leads to a dramatic improvement for, e.g., multi-campaign analyses or the management of permanent arrays. New parameters (e.g., station velocities) may be set up in ADDNEQ. Bernese GPS Software Version 4.2 Page 1

22 1. Introduction and Overview The ionosphere modeling part was completely revised [Schaer et al., 1995], [Schaer et al., 1996]. Version 4.0 allows to produce regional or global ionosphere models which may be used to resolve the initial phase ambiguity parameters even on baselines up to 2000 km [Mervart, 1995]. The model parameters are established using the double-difference phase observable. Version 4.0 contains options to process special pseudo-kinematic data in the post-processing mode. The Bernese Processing Engine, developed together with Ch. Rocken and J. Johnson from UCAR, is particularly well suited to process data from permanent GPS arrays in a completely automatic and very efficient way. The documentation consists of two components: there are help panels accompanying (almost) every panel of the Version 4.0 menu system. In addition there is the off-line documentation focusing on theory, models, and on commented typical applications. Last but not least it should be mentioned that the processing speed of Version 4.0 could be improved by about an order of magnitude in programs GPSEST and ADDNEQ. Version 4.0 is designed to be used for big networks ( receivers), too. The enhancements of Version 4.2 with respect to Version 4.0 are: Capability to process not only GPS, but also GLONASS observations stemming from GLONASS or combined GLONASS-GPS receivers. Very much improved capabilities to process undifferenced observations to allow for satellite and receiver clock estimation and to enable time and frequency transfer (see Chapter 16). Capability to process SLR observations to GPS and/or GLONASS satellites. Improved troposphere modeling and estimation (see Chapter 12). Elevation dependent weighting of observations is possible. In addition to the program ADDNEQ, which, as mentioned above, was an essential new tool of Version 4.0, the new program ADDNEQ2 is included (description see Chapter 19). The new program and the menu program associated with it are written in Fortran 90 and therefore require a Fortran 90 compiler. ADDNEQ2 may be characterized as follows: Consequent use of Fortran 90 features, Consequent use of transformations of parameters (instead of weighting), Identical treatment of all parameter types (step-wise linear functions of time), Many new options. Eventually, ADDNEQ2 will totally replace ADDNEQ. Program ADDNEQ is mainly included for those users of Version 4.2 not yet having access to Fortran 90. Version 4.2 of the Bernese GPS Software is a tool meeting highest accuracy standards. Typical users are: Scientists using it for research and education, Survey agencies responsible for high-accuracy GPS surveys (e.g., first order networks), Page 2 AIUB

23 1.2 Main Objectives and General Characteristics Agencies responsible to maintain arrays of permanent GPS receivers, Commercial users with complex applications demanding high accuracy, reliability, and high productivity. The software package is particularly well suited for: Rapid processing of small-size single and dual frequency surveys (typical example included in documentation), Permanent network processing, Ambiguity resolution on long baselines (up to 2000 km using high accuracy orbits), Ionosphere and troposphere modeling, Clock estimatino and time transfer, Combination of different receiver types (taking into account antenna phase center variations), Simulation studies, Orbit determination and estimation of Earth rotation parameters, Generation of so-called free network solutions. General features of the software are: All principal observables recorded by high-accuracy geodetic GPS and GLONASS receivers may be processed (code and phase data on both carriers, see next section). Six different linear combination of L1 and L2 may be used (see next section). Data from various receiver types may be processed and combined in the same processing steps (this includes the establishment and the use of receiver-type specific antenna phase center variations). Single and dual frequency data may be processed in the same estimation step, ionosphere models may be used to minimize the impact of ionospheric biases on coordinates. The parameter estimation programs GPSEST, ADDNEQ, and ADDNEQ2 may be used for baseline-, session-, campaign-, and multiple-campaign processing. ADDNEQ and ADDNEQ2 make it possible to generate many different complex solutions (e.g., annual coordinate- and ERP-solutions) using, e.g., daily normal equation systems without having to re-process observations. A big variety of parameter types may be solved for simultaneously. The observations, broadcast ephemerides, etc., are passed to the Bernese GPS Software uniquely through the RINEX format, (the Receiver INdependent EXchange format, see [Gurtner, 1994]). It may thus be said that data from all receiver types for which a RINEX interface exists, may be processed by the Bernese GPS Software. Table 1.1 gives an impression of the receiver types which have actually been successfully handled by Version 4.2 of the software package. Let us point out once more, however, that data from every receiver type may be processed, provided its data are available in RINEX files. Bernese GPS Software Version 4.2 Page 3